Re: Locomotive Construction

South Park Wrote:
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> So, ... am I following this logic to assume a
> 2-8-0 would be able to have an even lower firebox
> ?
No, you can't hang the firebox off the back of the engine with no supporting wheels underneath (except for some very small narrow gauge engines). The engine's rear-most axles would be overloaded, the boiler might be subject to unacceptable strains, etc.

> On the GW No.90 pictured above, why were the
> drivers not sized larger for greater speed, or the
> boiler diameter increased for greater steam
> capacity ?

The chosen driver size was adequate for the speeds that were required of the engine. Driver size is a compromise between the starting tractive effort, low-speed pulling power, required top speed, adequate size for the desired engine stroke, adequate room for counterweights, keeping the wheelbase within limits, and the overall height of the engine. The engineers had to juggle a lot of considerations.

Same thing with the boiler- it provided adequate steaming capability for the engine's intended service. A bigger boiler would cost more (maybe more than the railroad was willing to pay) and would increase the weight of the engine (likely above the desired axle loads).

> Thanks again for your patience with this
> neophyte.

Glad to help.

Hugh "Low Water" Odom
The Ultimate Steam Page
[www.trainweb.org]